Fluid circulating method and system for wells

ABSTRACT

A system and apparatus for circulating well fluids in a well having a U-tube flow path therein, wherein the well fluids are utilized to pump loading fluids or dead or gas-free fluids into the well to kill the same, or to circulate well tools in the flow conduit by the pump-down through the flow line method without wasting the circulating fluids, or to displace the circulating fluids from the well, and to load the well with a loading fluid to perform other operations thereon. The well fluids may be used as a source of power for operating the pump of a system, and a hydraulic fluid pump may be utilized, or pressure from another source may be utilized, for operating the pump to circulate the fluids in accordance with the invention.

United States Patent Sizer [54] FLUID CIRCULATING METHOD AND SYSTEM FOR WELLS [72] Inventor: Phillip S. Sizer, Dallas, Tex.

[73] Assignee: Otis Engineering Corporation, Dallas, Tex. [22] Filed: July 8, 1970 [21] Appl. No.: 53,186

[52] U.S.Cl ..166/313, 166/314, 166/685 [51] Int. Cl ..E21b 43/00 [58] Field ofSearch ..l66/3133l5,6768.5,

[151 3,654,995 [451 Apr. 11,1972

Primary Examiner-lames A. Leppink Attorney-43. Hastings Ackley [57] ABSTRACT A system and apparatus for circulating well fluids in a well having a U-tube flow path therein, wherein the well fluids are utilized to pump loading fluids or dead or gas-free fluids into the well to kill the same, or to circulate well tools in the flow conduit by the pump-down through the flow line method without wasting the circulating fluids, or to displace the circulating fluids from the well, and to load the well with a loading fluid to perform other operations thereon. The well fluids may be used as a source of power for operating the pump of a system, and a hydraulic fluid pump may be utilized, or pressure from another source may be utilized, for operating the pump to circulate the fluids in accordance with the invention.

13 Claims, 4 Drawing Figures PATENTEDAPR 11 I972 3.654895 sum 1 OF 3 INVENTOR. Pam/P 6? 5/250 BY {Z/W W 'ATTORMFY FLUID CIRCULATING METHOD AND SYSTEM FOR WELLS This invention relates to new and useful improvements in well fluid circulating systems and methods.

It is one object of the invention to provide a new and improved method and system for circulating well fluids into and through a well having a U-tube flow path system therein.

It is a particular object of the invention to provide a system and method of circulating well fluids into and through a well having a U-tube flow conduit pattern therein wherein the fluid pressure of the producing well fluids is utilized to circulate dead or gas-free fluids in the well for loading or killing the well, for circulating well tools in the well U-tube system by the pump-down through the flow line method, or for displacing the dead fluids so used by another fluid, such as a loading fluid, to perfonn other operations on the well.

It is a still further important object of the invention to provide a method and a system of the character described wherein the well fluids are used for power for circulating the dead fluids, and a less powerful and less expensive pumping system is needed for supplementary use in injecting the dead fluids into the well, whereby a small portable pump may be used for this purpose.

Another object of the invention is to provide a method and a well fluid circulating system which is operable to accomplish the results outlined in an economical manner with a minimum of auxiliary power equipment.

Still another object of the invention is to provide a fluid circulating system wherein a pump is included in the system,

which pump is operated by fluid pressure from the well producing formation for circulating gas-free or dead loading or operating fluids into the well.

Another particularly important object of the invention is to provide a system and method of circulating fluid in a well having a U-tube flow circuit therein wherein a circulating pump is connected in a closed continuous path or circuit with the U- tube conduits in the well, whereby operating fluids may be circulated in the U-tube flow path in the well with a minimum of power and equipment.

Still another object of the invention is to provide a system and method of operating a well for circulating well fluids in a well of the character just described wherein the fluids may be circulated by said pump in the closed circuit regardless of the elevated formation pressure applied to the circulating fluids, whereby the fluids may be circulated at an elevated pressure resulting from the formation pressure being applied to such fluids, or when the pressure is elevated as a result of the use of an accumulator or similar pressure maintainer connected in the system.

Still another object of the invention is to provide a system of the character described wherein the gas-free or dead operating fluids may be circulated in the system without application of the pressure of said operating fluids to the producing formation.

The invention is, therefore, directed toward the provision of a well fluid circulating method and system wherein the energy of the producing formation fluids is utilized to operate a pump for introducing dead, or unaerated, or gas-free liquid into the well system for the purpose of use as an operating fluid for pump-down tool through the flow line tool operations, or for loading the well to kill the same, whereby a minimum amount of additional power or auxiliary power is required for operation of the system to load the well flow conduit system and to circulate the fluids therein or to kill the well.

Additional objects and advantages of the invention will be readily apparent from the reading of the following description of a device constructed in accordance with the invention, and reference to the accompanying drawings thereof, wherein:

FIG. 1 is a schematic flow diagram of a well fluid circulating system and apparatus used for practicing the method of circulating a gas-free loading fluid or liquid into the well flow conduit for carrying out the purposes of the invention;

FIG. 2 is a view similar to FIG. 1 showing the system in condition for circulating the gas-free liquids in a closed continuous path or circuit through the U-type flow conduit path in the well; I

FIG. 3 is a view similar to FIG. 1 showing the system and apparatus in condition for circulating a gas-free fluid into the well conduit U-tube system while displacing the fluids present in the system to another point of disposal; and,

FIG. 4 is a fragmentary view of the well head of the system showing lubricators for inserting pump-down through the flow line equipment into the well system for use therein.

In the drawings, FIG. 1, a well 10 having casing 11 disposed therein in the usual manner, with a well heat 12 at its upper end,'has a pair of flow conduits or conductors or tubing strings l3 and 14 which extend downwardly from the well head in the well bore to a cross-over flow conductor 15 located in the well near the lower end thereof and providing communication between the two conductors or tubing strings. A back-flow check valve 16 is disposed in the conductor 13 and a similar back-flow check valve 17 is provided in the conductor 14, both check valves being located below the cross-flow passage 15. A lateral flow conduit 18 is connected to the upper end of the well casing communicating with the annular space between the casing and the tubing strings and a valve 19 is connected therewith for controlling admission of fluids into or flow of fluids from the annulus in the usual manner. If desired, a well packer (not shown) may be provided in the well for sealing between the casing and the tubing strings l3 and 14 in the usual manner.

A pair of surface flow lines 22 and 23 connected with the upper ends of the tubing strings 13 and 14 respectively lead therefrom to a well flow directing manifold system 21. The flow controlling system and apparatus of the invention is connected with the manifold and is designated generally by the numeral 20.

The manifold is shown as constructed in substantially a square flow path, having a pair of divergent conduits 25 and 26 connected with each other and with the surface flow line 22 and the tubing string 12, and another pair of divergent conduits 27 and 28 are connected with each other and with the surface flow line 23 and the tubing string 14. The ends of the conduits 25 and 27 are connected together and to an elongate conductor 29 leading to the flow controlling system 20 of the invention, while the ends of the conduits 28 and 26 are connected to each other and to a similar conductor 30 which also leads to the flow controlling system 20.

A valve 31 is connected in the conduit 25 between the ends thereof for controlling flow through the conduit 25. Similarly, a valve 32 is connected in the conduit 26 between its ends for controlling flow through that conduit. Also, a valve 33 is connected in the conduit '27 between its ends for controlling flow through such conduit, and a valve 34 is connected in the conduit 28 for controlling flow therethrough.

It will therefore be seen that by manipulation of the valves 31, 32, 33 and 34, flow from the conductor 30 may be directed, as shown in FIG. 1, through the conduit 28 and valve 34 of the manifold to the flow line 23 and then to the tubing string 14 in the well. The fluids will then flow downwardly in tubing string to the cross-flow passage 15 thence upwardly through the tubing string 13 to the surface, the fluids being prevented by the back-flow check valves 16 and 17 from entering the well producing formation therebelow. At the upper end of the tubing string 13 the fluids will flow into the surface flow line 22 and thence through the manifold conduit 25 and the valve 31 to the conductor 29, through which they will flow to the flow control system of the invention. The valves 32 and 33 are closed to prevent flow through the conduits 26 and '27 and to maintain flow in the path described. To reverse flow, if desired, the valves 32 and 33 may be moved to the open positions (not shown) and the valves 31 and 34 moved to the closed positions (not shown), whereupon fluid flowing from the conductor 30 will pass through the manifold conduit.26 and valve 32 to the surface flow line 22 and thence into the tubing string 13. The fluids will then flow downwardly through the tubing string through the cross-flow passage 15 into the tubing string 14 and then upwardly and outwardly through the flow line 23 to the manifold 21, where the fluids will be directed through the conduit 27 and valve 32 to the conductor 29 leading to the flow control system 20. The valves 31 and 34 being closed, while the valves 32 and 33 are open, provide for this reverse circulation of fluids in the U-tube flow path formed by the tubing strings and the cross-flow passage 15.

The flow controlling apparatus and system includes a conductor having an adjustable choke 41 connected therein and leading from the conductor 29 to one port of a three-way valve 42, which has a second port thereof connected by a delivery conductor 43 from the discharge of a hydraulic fluid pressure pump 44 driven by a motor 45 in the usual manner. The hydraulic fluid pressure pump has a suction line 46 connected therewith leading into a hydraulic fluid storage or supply tank 47. The third port of the three-way valve 42 is connected with a pressure supply conductor 50 which leads to one port of a four-way valve 51 having two other opposed ports connected to conduits 52 and 53, respectively, leading to a fluid pressure power operator device used to operate a pump 70. The fluid pressure power operator device includes a cylinder 61 having a piston 62 movable therein by fluid pressure entering chambers 63 and 64 in the cylinder on opposite sides of the piston 62 through the conduits 52 and 53 respectively as will be explained. Movement of the piston by fluid pressure acting thereon moves a connecting rod 65 which has one end connected to the power piston 62 and the other end connected to a pump piston 72 slidable in a pump cylinder 71 ofa pump 70.

The other port of the four-way valve 51, opposite the port connected to the supply conductor 50, has a conductor 55 connected thereto which leads to one port of a three-way valve 56 having another port connected to a conduit 57 forming a return line to the hydraulic fluid tank 47. The third port of the valve 56 is connected to a discharge conductor 58 which leads to a conductor havingan adjustable choke 81 connected therein between the discharge conductor 58 and a separator 83. The fluid outlet of the separator is connected by a discharge or outlet conduit 84 to a tank or container 85 in which fluids from the well may be stored in the usual manner. A gas vent or conduit 86 leads from the upper end of the separator for disposing of the gas separated from the liquids from the well formation to a flare, a gas gathering line, or other usual disposal.

One port of a valve 82 is connected to the conductor 80 on the opposite side of the connection thereto of the discharge conductor 58 from the choke 81, and the valve 82 has its other port connected to a fluid pickup conductor 90 which leads to one port of a four-way valve 91. The opposite port of the fourway valve is connected to a supply conductor line 92 which leads to a pair of inlet conduits 93 and 94, and communicating with the chambers 73 and 74, respectively, in the pump cylinder 71 on the opposite sides of the pump piston 72. A check valve 95 is connected in the inlet conduit 93 and a check valve 96 in the inlet conduit 94 for preventing backflow of fluid pressure from the pump through the inlet conduits to the supply line 92. An outlet conduits 98 and 99 are connected to the chambers 73 and 74, respectively, in the pump cylinder on opposite sides of the piston 72 and each of the outlet conduits is connected to a return flow line or conductor 100 which is connected to the conductor 30 from the manifold, and a back-flow check valve 102 is connected in the outlet conduit 98 and a similar back-flow check valve 103 in the outlet conduit 99 from the pump to prevent back-flow of fluids from the flow line 100 into the pump cylinder. An accumulator or pressure surge tank 101 may be connected in the flow line 100 downstream of the pump to smooth out, reduce or eliminate pump pressure pulses in the system which might tend to loosen connections or break conduits.

The valve 91 has one of the two opposite ports thereof not connected with the conductors 90 and 92 connected to a circulating conductor 105 which leads to the flow conductor 40 from the well head manifold 21, while the other of the opposed ports is connected by means of an intake conductor 106 leading to a supply tank of storage tank 110 for containing fluids to be introduced into the well, such as gas-free oil, loading fluids, mud, or the like.

As the fluid pressure in the power cylinder moves the piston from one end thereof to the other, the connecting rod 65 is moved therewith and an operator rod secured to the con necting rod engages, at alternate ends of the stoke of the piston, one of the longitudinally spaced operating lugs or dogs 116 and 117 carried by a valve actuator member 1 18. The valve actuator member is connected at one end to the operating handle of the four-way valve 51, whereby when the actuator member 1 18 is moved to the right by engagement of the operator rod 115 with the dog or lug 116 as the connecting rod moves to the right, the valve operating handle 120 is moved to the right to the position shown in FIG. 1 the core or closure member of the valve 51 in position to communicate the conduit 50 with the conduit 52 and to communicate the conduit 53 with the conductor 55. When the valve piston 62 is moved to the left, the operator rod 115 is moved to the left to engage the lug or dog 117 and move the valve actuator member 118 to the left to swing the valve handle 120 to the left to the position, shown by dotted lines, wherein the core of closure member of the valve 51 is moved to a position in which the flow passages in the closure member are disposed to communicate the conductor 50 with the inlet conduit 53 to the chamber 64 in the cylinder of the power operator device, while the conduit 52 from the chamber 63 of the cylinder 61 of the operator device is connected to the conductor 55. The functioning of this structural arrangement will be further explained hereinafter.

In the operation of the system, when the well flow conductors are full of fluid from the producing formation below the check valves 16 and 17 and it is desired to pump dead or gasfree oil or other fluid into the tubing strings for the purpose of circulating pump-down equipment in the well, or loading the well, or for other purposes in which it is desired that the strings be loaded or filled with gas-free oil or the like, the system is arranged in the manner shown in FIG. 1, with various components of the well head manifold 21, and the flow controlling system and apparatus 20, in the positions shown therein.

In operation under this arrangement, fluid from the well producing formation will flow upwardly in the tubing string 13 past the check valve 16, and will flow upwardly in the lower portion of the tubing string 14 past the check valve 17 and through the lateral or cross-flow connector 15 into the tubing string 13 above the check valve 16. However, when the system is in operation, the check valve 17 will be closed to prevent back-flow of fluids from the tubing string 14 into the well producing formation connected therewith, so that the usual procedure is for the well fluids from the'producing formation communicating with the flow tubing string 13 to flow upwardly therein past the check valve 16 to the flow line 22 at the surface. From the flow line 22, the fluids will pass through the manifold conduit 25 and the open valve 31 into the conductor 29 and thence to the flow control system apparatus. The valve 32 in the manifold conduit 26 being closed, and the valve 33 in the manifold conduit 27 being closed, the fluids will be directed as stated. From the conductor 29, the fluids will flow through the flow conductor 40 and the adjustable choke 41 to the three-way valve 42, which is then in a position connecting the conductor 40 with the conductor 50 leading to the four-way valve 51. The well fluids will be directed from the conductor 50 through the four-way valve to the conduit 52 and therethrough to the chamber 63 of power operator cylinder 61 on the right hand side of the piston 62, where the pressure of such well fluids will move the piston to the left and discharge any fluids in the chamber 64 of the cylinder to the left of the piston outwardly through the conduit 53 and through the closure member of the valve 51 to the conductor 55 connected with the three-way valve 56, which is in a position directing flow from the conductor 55 to the discharge conductor 58 which leads to the conductor 80 and through the adjustable flow controlling choke 81 to the separator 83. Here, the liquids are separated from the gas, the gas being vented or otherwise disposed of through the vent conduit 86 and the liquids being collected in the storage tank or container 85 after having been discharged through the outlet conductor 84 into the tank.

As the piston 62 of the power operator member 60 is moved to the left by the well fluid pressure in the chamber 63, the connecting rod 65 moves the piston 72 of the pump to the left in the pump cylinder 71 and discharges any fluid present in the chamber 74 of the cylinder outwardly through the outlet conduit 99 past the check valve 103 to the return flow conductor 100, which is connected with the conductor 30 extending to the well head manifold 21. At the well head manifold, the fluids from the conductor 30 are directed through the manifold conduit 28 and the open valve 34 to the surface flow line 23, and then into the upper end of the tubing string 14, then downwardly in the well through the tubing string 14 to the cross flow passage 15, where the fluids again enter the tubing string 13. The storage chamber or accumulator 101 smoothes or levels out the pressure pulsations in the fluid from the pump as it is delivered therefrom through the return flow conductor 100 and the conductor 30 to the well head manifold.

As the connecting rod moves to the left as a result of the action of the well fluids in the chamber 63 on the piston 62, the connecting rod 65 is moved to the left to move the operator rod 115 carried thereby to the left until it engages the lug or dog 117 on the valve actuator member 118, and then moves the actuator members to the left to swing the valve handle member 120 to the left to the position shown in dotted lines. In this position, fluids from the tubing string 13 passing through the manifold conduit to the flow conductor 40 and the conductor 50 to the four-way valve 51 will be directed by the flow passages in the closure member of the valve to the conduit 53 leading into the chamber 64 on the left side of the piston 62 in the cylinder 61 of the fluid pressure power operator device 60. The well fluid pressure then moves the piston 62 to the right, which will displace any fluids remaining in the chamber 63 outwardly through the conduit 52 and through the four-way valve 51 to the conductor 55 and the discharge conductor 58 and conductor 80 to the separator, where gas is discharged through the vent and fluids through the outlet conductor 84 into the tank or storage container 85.

The continued movement of the operator power piston 62 to the right moves the connecting rod 65 to the right and so moves the pump piston 72 to the right in the pump cylinder 71 and discharges fluids present in the chamber 73 of the cylinder outwardly through the outlet conduit 98 past the check valve 102 into the conductor 100, and thence through the conductor to the well head manifold 21 and through the manifold conduit 28 and the flow line 22 into the tubing string 14 to introduce dead or gas-free oil or loading fluid from the supply tank 110 into the tubing string.

As the pump piston 72 moves to the right in the cylinder 71, additional loading fluid or oil is drawn into the chamber 74 of the cylinder on the left hand side of the piston, from the storage tank 110 by way of the intake conductor 106 which is in communication through the four-way valve 91 with the supply conduit 92, the fluid being drawn through the inlet conduit 94 into the cylinder past the back-flow check valve 96. Since the pressure in the chamber 73 of the cylinder 71 is elevated, the check valve 95 in the inlet conduit 93 is closed and the fluids contained in the chamber 73 will be forced under pressure outwardly through the outlet conduit 98 past the check valve 102, in the manner just described.

From the foregoing, it will be seen that for each stroke of the piston 62 of the power operator device 60, a volume of loading fluid, dead oil or gas-free fluid of any desired type, will be withdrawn from the storage tank 110 and introduced through the pump cylinder 71 and the return flow conductor 100 to the well head manifold 21, where it is directed into the tubing string 14.

Since the area of the piston 62 of the power operator device 60 is substantially larger than the area of the pump piston 72, it will be seen that the pressure of the well fluids flowing from the well may be utilized to introduce the loading fluid, dead oil, or other gas free liquid, into the well with a minimum of additional power required. Substantially no added power will be required until a condition of substantial equilibrium in the U-tube has been reached between the pressure in the producing formation communicating with the tubing 13 and the pressure in the tubing 14. Repeated strokes of the piston 62 of the power operator device 60 will cause repeated strokes of the pump piston 72 and inject additional volumes of fluid from the storage tank 110 into the well conduit U-tube formed by the tubing string 14, the cross-flow passage 15 and the tubing string 13 connected with the well head manifold 21, and eventually the U-tube well conduit system will be loaded with the gas-free oil or other desired suitable operating fluid, the pressure of the producing fluids from the well being utilized to effect such loading, while the fluids from the well are discharged from the cylinder of the power operator member 60 through the conduit 58 to the separator 83, where the gases are separated from the liquids and the liquids are conducted through the outlet conduit 84 into the storage tank 85 and the gas is vented or otherwise disposed of through the conduit 86. The valve 82 is closed to direct the fluids flowing through the conduit 58 into the conduit past the adjustable choke 81 to the separator. The valve 82 being closed also prevents well fluids from the tubing string 13 passing through the well head manifold and the conductor 29 to the conductor 40 from flowing through the conductor 105 and the valve 91 to the separator.

It will be seen, therefore, that the system described provides for utilization of the well producing formation pressure for actuation of the pump for introducing a gas-free or dead oil loading fluid or operating fluid into the U-tube flow conduit system of the well, to substantially fill the same.

When a condition of substantial equilibrium between the flowing well fluids and the loaded loading fluids or gas free liquids inserted into the well has been attained, so that the well fluid pressure does not work the operator device 60 and the pump 70, additional liquids are pumped into the well by means of the hydraulic fluid pressure pump 44 driven by the motor 45 to pump hydraulic operating fluid in a closed circuit to actuate the piston 62 of the operator device 60 to drive the pump piston 72 to inject additional liquid into the U-type system in the well.

The valve 42 is moved to connect the hydraulic pump delivery conductor 43 with the conductor 50 leading to the four-way valve 51. Similarly, the valve 56 is turned to connect the conductor 55 with the return line conductor 57 to the tank 47, from which the hydraulic operating fluid is drawn. Also, the valve 82 is turned to the open position to permit well fluids flowing upwardly through the tubing string 13 and the surface flow line 22, through the manifold conduit 25 and the conductors 29 and 40, to flow through the circulating conductor 105 and the valve 91 to the conductor 90 and through the valve 82 to the discharge conductor 80, then through the choke 81 to the separator 83 and thence to the container or tank 85 and the gas vent or disposal line 86.

In this case, the pump will operate to draw up hydraulic fluid through the suction line 46 from the supply tank 47 and direct the fluid under pressure through the delivery conductor 43 to the valve 42, from which the hydraulic fluid is directed through the conductor 50 to the four-way valve 51, where it will act in the manner already described to operate the power piston 62 in the power cylinder of the power operator device. Hydraulic fluid discharged from the cylinder will pass outwardly through the conduit 53 and the valve 51 to the valve 56, and then back through the return line 57 to the supply tank.

The operation of the piston is identical to that of the form first described, the valve 51 being shifted by the valve actuator for each stroke of the power piston. Well fluids withdrawn through the tubing string 13 will pass through the manifold 21 to the conductor 29, the flow conductor 40 and the circulating conductor 105, then through the valve 91 and the conductor 90 to the open valve 82, and through the conduit 80 past the adjustable choke 81 to the separator where the liquids are delivered through the outlet conductor 84 to the storage tank or container 85 and the gases are disposed of through the vent or disposal conduit 86. Since the three-way valve 56 has been moved to the position connecting the conductors 55 and 57, the discharge conductor 58 is closed and well fluids will be directed through the circulating conductor for disposal in the manner just described.

The loading fluid, which may be gas-free oil, or any other fluid of the type already described as being injected in the well, will be picked up from the tank 110 through the intake conductor 106 and the supply conductor 92 to the pump inlet conduits 93 and 94 through which the fluid enters the pump cylinder. The fluid will then be pressed out of the chambers of the pump cylinder through the output lines 98 and 99 past the check valves 102 and 103, respectively, and through the return flow conductor 100 and past the accumulator 101, which reduces pressure surges or pump pressure vibrations in the flow lines, through the conductor 30 and the manifold conduit 28 connected by means of the surface flow line 23 to the upper end of the tubing string 14. In this manner, the gasfree loading fluid may be pumped from the supply tank 110 into the well until both the tubing strings of the U-tube system are completely full, and the entire manifold and flow controlling system is full of the loading fluid.

During the operation just described, the well is loaded with a gas-free liquid or dead liquid. The flow controlling system may then be altered to that shown in FIG. 2, wherein the fluids in the tubing strings are circulated in a closed circuitous path through the U-tube conduit system of the well and through the pump 70 back into the well. The power operator device 60 may be driven by means of the hydraulic fluid pump 44 drawing hydraulic fluid from the tank 47, in the manner just described. In this case, however, the valve 82 will be closed and the four-way valve 91 will be turned to the position in which the circulating conductor 105 is connected with the supply conductor 92 to the pump 70, whereby the gas-free fluids coming from the well tubing string 13, through the manifold 21 and the conductors 29, 40 and 105, will be directed to the supply conductor 92 and through the pump inlet conduits 94 and 95 into the pump. The gas-free fluid is then displaced out of the pump through the outlet conduits 98 and 99 to the return flow conductor 100 and through the conduit conductor 30 to the manifold 21 to pass through the manifold conduit 28 and the surface flow lines 23 to the tubing string 14, then back down the well bore in the tubing string to the cross-flow conduit 15 at the bottom of the U-tube system in the well. It will be seen, therefore, that the fluids in the well, comprising dead liquids or gas free liquids such as gas free oil, may be circulated in a closed circuit through the tubing string U-tube flow path in the well.

The direction of flow of the fluids in the well may be varied from that shown in FIG. 2 to the reverse direction, so that the fluids are pumped into the well through the tubing string 13 and out of the well through the tubingstring 14. This is accomplished by closing the valve 31, opening the valve 32, closing the valve 34, and opening the valve 33. With the valves in this condition, fluid pumped to the return flow conductor 100 from the pump 70 will pass through the conductor 30 into the well head manifold 21, where it will flow through the manifold conduit 26 and the valve 32 to the surface flow line 22 connected to the upper end of the tubing string 13. The fluids will then flow downwardly through the tubing string 13, through the cross-flow member 15 and then upwardly through the tubing string 14 and the flow line 23 to the well head manifold, where they will flow through the manifold conduit 27 past the valve 33 and through the conductor 29, the flow conductor 40 and the circulating conductor 105 to the valve 91, and then be returned through the supply conductor 92 to the inlet conduits 93 and 94 for the pump. The position of the valves in the well head manifold 21 for reverse circulation in this manner is shown in dotted lines in FIG. 2.

It will be seen, from the foregoing, that the dead fluid or gasfree oil may be utilized to circulate pump down well tools, or through flow line well tools, into and out of the well tubing strings of the U-tube flow path by means of the oil or other liquid present in the system by merely controlling the direction of flow of the fluids by means of the valves in the well head manifold 21.

The pump 44 may be utilized to produce as high a pressure as desired, but since the area of the piston 62 of the power operator device 60 is larger than the piston 72 of the pump 70, a lesser pressure is needed to move the oil through the system than would be needed to displace fluids from the well. Also, during this operation the check valves 16 and 17 below the cross-flow passage member 15 will remain closed, so that the fluid pressure of the circulating operating fluid in the system will not be applied to the well producing formation. Should the well not have the check valves below the cross-flow passage, the pressure in the system may be elevated to a sufficient value to slightly overcome the well formation pressure to maintain a slight back pressure on the fluids in the well formation while circulating the gas-free operating fluid. It is preferable that the check valves be utilized in the system to prevent escape of the operating fluid from the closed system to the well formation.

A well head lubricator system connected between the manifold 21 and the upper ends of the tubing strings, for use in inserting pump down well tools into the U-tube flow conduit system, is shown in FIG. 4, wherein a valve is connected to the upper end of the tubing string 13 and to the end of an arcuate radius flow tube 151 connected at its other end to a lubricator having a closure 161 at the opposite end through which well tools may be inserted into the lubricator while the valve 150 is closed for insertion into the well. A valve 155 is connected in the surface flow line 22 between the lubricator and the well head manifold 21, so that the lubricator may be completely isolated during the time that the same is open for insertion of well tools thereinto or removal of well tools therefrom. Similarly, a lubricator may be connected to the upper end of the tubing string 14. In this case, a valve will be connected to an arcuate radius flow tube 181 connected at its other end to one end of the lubricator 170 having a closure 171 at its other end. A valve 185 will be connected in the conductor 23 between the lubricator and the well head manifold 21. The lubricator closure cap 171 may be removed to open the lubricator to insert or remove well devices. While .the cap 171 is removed from the lubricator 170, the valves 180 and 185 are closed to isolate the lubricator from the flow line system. With the well conductor system in the circulating path shown in FIG. 2, the lubricator 170 will be used to insert well devices into the tubing string 14. When the system is in the position for reverse flow and the valves of the manifold 21 are in the position shown in dotted lines in FIG. 2, the lubricator 160 will be utilized to insert and remove well tools into and from the tubing string 13 by the usual pump down through the flow line operating devices.

From the foregoing, it will be seen that the system provides for circulating gas-free operating fluids through the well U- tube flow conduit system in either direction, and that suitable well tools may be inserted into and removed from either of the flow conductors or tubing strings 13 or 14 by means through the flow line pump down tool operating mechanisms in the usual manner. It will also be seen that the device is operable by a low pressure high volume pump 44 connected to the fluid pressure power operator device 60 for driving the pump 70 to circulate the fluids in the system. Thus, very little horsepower will be required for effecting circulation of the fluids, since the liquid returning from the well is not allowed to lose its pressure but is directed back through the pump where it will be discharged into the well U-tube flow path system again. The pump 44 is merely utilized to circulate the fluid, at whatever pressure the fluids are under while in the closed system. The actual pressure of the fluids in the system may be quite high, but the pressure necessary to circulate the fluids by means of the pump 44 is very low, and the horsepower requirements are low, so that a small hydraulic pump may be utilized to effect that circulation.

Should it later be desired to utilize the system for flowing well fluids or for other well operations after the pump down well tools have been installed, the operating fluid consisting of the gas-free oil or other dead liquids may be circulated out of the system with the system arranged in the manner illustrated in FIG. 3.

In this type operation, the power operator device 60 is actuated by the hydraulic fluid, using the pump 44 in the manner just described. However, the four-way valve 91 is returned to the position in which the supply conduit 92 to the pump 70 is connected with the suction or intake line 106 to the tank 110, whereby loading fluids such as mud or water, or other fluids, may be picked up by the well fluid pump 70 and injected or pumped into the well. The hydraulic pump 44 and the well fluid pump 70 will be actuated in the manner just described for circulating the fluids in the closed system. However, the fluids injected into the well will be the fluids from the supply tank 110, which will pass through the pump 70 and the return flow conductor 100 and conductor 30 to the well head manifold 21, where they will pass through the manifold conduit 28 and the valve 34 to the flow line 23, and then into the upper end of the tubing string 14 and downwardly therein in the well bore. Well fluids from the producing formation connected with the tubing string 13 will flow upwardly through the tubing 13 to the flow line 22 and the well head manifold 21, and will flow by way of the manifold conduit 25 through the valve 31 to the conductor 29 and the flow conductor 40 to the circulating conductor 105 connected to the four-way valve 91. In this operation, the four-way valve 41 is moved to the position connecting the circulating conductor 105 with the conductor 90 and the valve 82 which is now open, so that the fluids from the well may pass therethrough into the discharge conductor 80 and past the adjustable choke 81 to the separator 83, where the liquids will be discharged through the conductor 84 into the tank or container 85 and gases will be disposed of through the gas vent 86. The loading fluid or the operating fluid in the tubing strings is thus displaced from the.

well bore, and a water or mud loading fluid from the supply tank 110 will replace the circulating fluid in the well system. Thereafter, the system may be returned to the arrangement shown in FIG. 1, wherein the pump may be utilized to pump the mud from the well in the manner described in connection with FIG. 1, and when the well has been unloaded the well may be produced in the usual manner through the manifold.

The producing formation may produce through the tubing string 13 to the manifold and then through the manifold to the separator in the manner just described. The loading fluid will remain in the tubing string 14 unless displaced therefrom by reverse circulation of fluids from the well producing formation through the system in the manner set out in connection with the arrangement shown in FIG. 1 wherein the well fluids will be utilized to pump the mud from the well upwardly through the tubing string 14 and the power operator device 60 through the discharge conductor 58 to the separator 83.

Suitable valving may be arranged in the cross-flow passage means 15 to close off the flow of fluids through that cross-flow path to maintain the loading fluid in the tubing 14 or to maintain loading fluid in the tubing 13 and produce from the other formation to which the well is connected, as desired.

While a dual string of tubing connected by a cross-flow passage device at their lower ends has been described, it is readily apparent that a U-tube path formed by tubing string and the annular space between the tubing and the well casing may be used equally well, as is well known to provide the desired in and out flow paths in the well. Also, other types of chokes than those described may be used, or they may be omitted, if conditions permit and it is desired.

From the foregoing, it will be seen that the system and apparatus of this invention provide useful means of pumping liquid into a well; that it utilizes the well fluids and the pressure of the well fluids for actuating the power operator device to drive the pump for injecting fluids into the well, such as gasfree operating fluids for use in pump down operations. It will also be seen that the well may be loaded or killed by injection of loading fluid into the well by means of the system, utilizing the hydraulic fluid pump for driving the power operator device. Also, it will be seen that the operating fluids may be injected into the well by actuation of the operator member 60 by well fluids until the operating fluid has substantially filled the system, then by low horsepower hydraulic fluid pump means to completely fill the system; that the operating fluid may easily be circulated at any desired pressure by means of the hydraulic fluid pump 44 actuating the operating device to operate the pump 70 to circulate the fluids in the closed circuit U-tube flow path system.

It will be seen also that pressure of the well fluids is at all times maintained under control, and that adjustable chokes may be used to regulate the fluids being pumped by the system to control the actuation of the system and to conserve the utilization of the energy of the well fluids from the well; that the system provides means for loading the well flow conduit system with actuating fluid, or loading or killing fluid, without wasting the energy of the displaced well fluids, as when the well fluids are vented or discharged into the atmosphere or through the usual flow lines. After a loading or operating fluid has been inserted into the system to completely fill the same, the fluids may be circulated in the system with a minimum amount of horsepower energy required to operate the hydraulic fluid pump 44 and circulate the fluids through the well U- tube flow conduit system, in either direction as controlled by the well head manifold 21. It is also readily apparent that one fluid in the well system can be replaced by another by pumping liquid into one leg of the tubing U-tube flow path system while discharging the other fluid from the other leg thereof into a suitable container.

It will thus be seen that the system, and the method of operating a well utilizing the system and apparatus, is useful for killing the well, circulating fluids in the well, for pump down operations, or for discharging one fluid in the system by means of another. It will also be seen that the system disclosed does not damage the well producing formation, since the check valves 16 and 17 below the cross-flow passage 15 prevent application of the operating fluid pressure to the well producing formations, and any of the fluids pumped into the well through the system will not enter the producing formations or contaminate or mingle with the well fluids in the formation.

The foregoing description of the invention is explanatory only, and changes in the details of the construction illustrated may be made by those skilled in the art, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed is:

1. A system for operating a well having U-tube flow path conduits therein including: fluid pump means; flow conductors connected to the upper ends of the U-tube flow conduits in the well for conducting fluids from one of the flow conduits in the well to the pump means and from the pump means back into the other conduit of the well for circulating fluids into and out of the U-tube flow path conduits in said well; means for controlling fluid flow through said conductors; fluid pressure operator means connected with the pump means for operating the pump means; means for conducting well fluids from one of the flow conductors connected to the flow conduits in the well to the operator means to drive the operator means to operate the pump means by well fluid pressure; a supply of fluids for insertion into the well; means connecting the supply of fluid for insertion into the well with the pump means, whereby the fluid from said supply is directed through the pump means into the other flow conductor and into the well flow conduits to fill the U-tube flow path conduits, the flow conductors connected to said conduits, the means for controlling fluid flow through said conductors, and the pump means with fluid from said source of supply of fluid; means for closing off the source of supply of fluid from the U-tube flow path conduits, the flow conductors connected thereto, and said pump means, and for directing well fluids flowing from the well flow conductors to the fluid pressure operator means for actuating the pump means to circulate the fluids therein through the U-tube flow path conduits, the flow conductors connected thereto and the pump means under well fluid pressure.

2. A system for operating a well having U-tube flow path conduits therein including: fluid pump means; flow conductors connected to the upper ends of the U-tube flow conduits in the well for conducting fluids from one of the flow conduits in the well to the pump means and from the pump means back into the other conduit of the well for circulating fluids into and out of the U-tube flow path conduits in said well; means for controlling fluid flow through said conductors; fluid pressure operator means connected with the pump means for operating the pump means; means for conducting well fluids from one of the flow conductors connected to the flow conduits in the well to the operator means to drive the operator means to operate the pump means by well fluid pressure; a supply of fluid for insertion into the well; means connecting the supply of fluid for insertion into the well with the pump means, whereby the fluid from said supply is directed through the pump means into the other flow conductor and into the well flow conduits; auxiliary pump means having auxiliary drive means operatively connected with said operator means for pumping auxiliary operating fluid to said operator means for actuating the same to operate said pump means when the well fluid pressure is insufflcient to actuate said operator means.

3. A well flow controlling system for use in operating a well having a U-tube flow path conduit therein, said system including: a flow direction controlling manifold at the surface connected to the upper ends of the U-tube flow path conduit for controlling the direction of flow of fluids into and out of said conduit; a source of supply of fluid to be injected into the well U-tube flow path conduit through the manifold; pump means connected to the source of supply of fluid and to the manifold for pumping fluid from the source of supply to the manifold and therethrough into the U-tube flow path conduit in the well; fluid pressure power operator means connected with said pump means for operating the pump means; means for conducting well fluid from the well through the flow directing manifold to the fluid pressure operator means for actuating said operator means by well fluid pressure to drive the pump means to pump fluid from the source of supply into the U-tube flow path conduit by means of said well fluid pressure to fill the U-tube flow path conduit, manifold and pump means with said fluid; means for closing off the source of supply of fluid from the U tube flow path conduit, manifold and pump means to provide a closed path in the well through the U-tube flow path conduit, manifold and pump means and for continuing to direct fluids flowing from the well to the operator means for operating said pump means by well fluid pressure to circulate the fluids in the closed flow path of the U-tube flow path conduit, manifold and pump means at the pressure of the fluids in the well; and means for conducting the well fluids passing out of said fluid pressure power operator means after operating the same to a place of disposal.

4. A system of the character set forth in claim 3 wherein: said pump means comprises a cylinder having a piston movable therein; an inlet fluid conduit connected with the source of supply of fluid; an outlet conduit from the cylinder to the flow directing manifold for conducting fluids from the cylinder to the flow directing manifold and to the U-tube flow path conduit in the well; and inlet and outlet conduits each having valve means therein controlling the flow of fluids into and out of the cylinder; and said fluid pressure operator means comprises a cylinder having a larger bore than the bore of the cylinder of the pump means; a piston movable in the cylinder of the operator means having an effective area larger than the effective area of the piston of the pump means; means connecting the power operator means piston with the piston of the pump means for driving the pump piston by means of the power operator means piston; means for conducting well fluids from the flow directing manifold connected with the well U-tube flow path conduit into the power operator cylinder for moving the piston therein to drive the pump means piston; and means connected to the cylinder of the power operator means for conducting the well fluids from said cylinder to said means for conducting said well fluids to a place of disposal after the power operator means piston has been actuated by said well fluids.

5. A system of the character set forth in claim 4 including: auxiliary pump means having auxiliary drive means operatively connected with said operator means for pumping auxiliary operating fluid to said operator means for actuating the piston of said operator means to operate said pump means when the well fluid pressure is insuflicient to actuate said operator means.

6. A well flow controlling system for use in operating a well having a U-tube flow path conduit therein, said system including: a flow direction controlling manifold at the surface connected to the upper ends of the U-tube flow path conduit for controlling the direction of flow of fluids into and out of said conduit; a source of supply of fluid to be injected into the well U-tube flow path conduit through the manifold; pump means connected to the source of supply of fluid and to the manifold for pumping fluid from the source of supply to the manifold and therethrough into the U-tube flow path conduit in the well; fluid pressure power operator means connected with said pump means for operating the pump means; means for conducting well fluid from the well through the flow directing manifold to the fluid pressure operator means for actuating said operator means by well fluid pressure to drive the pump means to pump fluid from the source of supply into the U-tube flow path conduit by means of said well fluid pressure; means for conducting the well fluids passing out of said fluid pressure power operator means after operating the same to a place of disposal; and auxiliary pump means having auxiliary drive means operatively connected with said operator means for pumping auxiliary operating fluid to said operator means for actuating the same to operate said pump means when the well fluid pressure is insufficient to actuate said operator means.

7. A well fluid circulating system for use with a well having conduits therein providing two separate longitudinal flow paths therein connected at their lower ends and having flow openings at their upper ends and providing a U-tube flow path conduit in said well communicating with at least one producing formation at the lower end of said well, said system including: a flow direction controlling manifold connected to each of the flow openings of the U-tube flow path conduit of the well and having means for controlling flow direction into and out of said U-tube flow path conduit; a circulating conductor connected to said manifold for receiving fluids from the U-tube flow path conduit in the well; a pump having a cylinder and a piston movable therein for pumping fluids; a supply conductor for conducting fluids to be pumped to the pump; a return conductor connected with the pump and with the manifold for conducting fluids to be pumped into the well from the pump to the manifold for direction into the U-tube flow conduit path in the well; a source of supply of fluid to be pumped into the well; means for disposing of fluids from the well; first valve means connected with the circulating conductor, with the supply conductor, with the source of supply of fluid to be pumped into the well and with the means for disposing of fluids from the well; said first valve means being movable to a first position connecting the supply conductor with one of either the source of supply of fluid to be pumped into the well or the circulating conductor connected with the manifold and connecting the means for disposing of fluids with the other of said source of supply of fluid to be pumped or said circulating conductor not connected with the supply conductor; said first valve means being movable to a second position connecting the other of the source of supply of fluid to be pumped or the circulating conductor with the supply conductor, and connecting the means for disposing of fluids with the one of said source of supply of fluid to be pumped and said circulating conductor not connected with the supply conductor; said first valve means when in one of said positions directing fluid from said source of supply of fluid to be pumped to said pump to be pumped into said well U-tube flow path conduit and when in the other of said positions directing fluid from one flow path of the well U-tube flow path conduit to said pump to be pumped into the other flow path of said well U-tube flow path conduit; a fluid pressure power operator device for operating the pump comprising: a cylinder with a power piston movable therein having a cross-sectional area greater than the cross-sectional area of the pump piston; said power piston being operatively connected with the pump piston for actuating the pump piston; second valve means connected with a pair of separate three-way valve means and with a pair of separate inlet conduits into the cylinder of the fluid pressure power operator device on the opposite sides of the power piston therein; one of said three-way valve means being also connected with said circulating conductor and with a supply line from a separate source of hydraulic fluid pressure, whereby when said one three-way valve means is in a first position well fluids from said circulating conductor are directed through said second valve means to said operator device for actuating the piston therein and said supply line from said source of hydraulic fluid pressure is closed, and when said one three-way valve means is in a second position hydraulic fluid pressure from said supply line from said hydraulic fluid pressure source is directed through said second valve means to said operator device for actuating the piston therein and said connection with said circulating conductor is closed; the other three-way valve means being also connected with said means for disposal of fluids and with a return line to said separate source of hydraulic fluid pressure, and movable to a first position to connect said second valve means with said means for disposal of fluids when said one three-way valve means is positioned to connect said second valve means with said circulating conductor whereby well fluids are directed to said operator device to actuate the power piston to operate the pump to pump fluid into the U-tube flow path conduit, and movable to a second position connecting said second valve means with said return line to said hydraulic fluid pressure source and to close the connection with said means for disposal of fluids when said one three-way valve means is positioned to connect said second valve means with said supply line from said source of hydraulic fluid pressure and said circulating conductor is closed, whereby hydraulic fluid pressure is directed through said second valve means to said operator device for actuating the power piston therein for pumping fluid into the U-tube flow path conduit in the well, and well fluids from said U-tube flow path conduit are directed to the means for disposal of fluids; and means connected with said power piston of said operator device for actuating said second valve means between positions connecting said one three-way valve means with said cylinder of said operator device alternately on opposite sides of said power piston in said cylinder in response to reciprocating movement of said power piston.

8. A system for circulating fluids in a well having conduits therein providing two longitudinal flow paths in said well connected near the bottom thereof to form a U-tube flow path for fluids in the well and comprising: pump means for pumping fluids into one of said conduits; operator means for said pump means; conduit means for directing well fluids from the other of said conduits to said operator means, said operator means being responsive to and driven by said well fluids from said other conduit; said pump means having a lesser operating area then the operating area of said pump means, whereby said operator means is operable by said well fluid pressure to operate said pump means to pump fluid into said one conduit;

auxiliary pump means having auxiliary drive means operatively connected with said operator means for pumping auxiliary operating fluid to said operator means for actuating said operator means for actuating said operator means to operate said pump means when said well fluid pressure is insufficient to actuate said operator means.

9. A system of the character set forth in claim 8 including: means for directing fluids pumped into said one of said conduits and into and from the other of said conduits to said pump means and through said pump means back into said one of said conduits in a closed circuit, whereby fluids may be circulated in said closed circuit to carry on pump down tool operations in said U-tube flow path.

10. A method of operating a well having a U-tube flow path conduit therein including: withdrawing well fluids from the well through one side of the U-tube flow path, utilizing said well fluids to actuate an operator device for operating a fluid pump; and pumping fluids by means of said fluid pump into the other side of the U-tube flow conduit; circulating fluids pumped into the well through said other side of said U-tube flow path into said one side of said U-tube flow path; shutting off flow of well fluids from the well to said operator device; and operating said operator device by a separate source of fluid pressure at the surface of the well to fill the U-tube flow path with liquids pumped thereinto from the surface by said pump.

11. A method of the character set forth in claim 10 including: the additional step of circulating liquids in the U-tube flow conduit in the well in a closed circuit through the pump.

12. A method of the character set forth in claim 11 including: the additional step of utilizing the circulating fluids in the closed system to carry out through-the-flow-line pump down tool operations in said U-tube flow path conduit.

13. A method of the character set forth in claim 10 including: the additional step of pumping another fluid into the U- tube flow path conduit to displace the fluid previously pumped into said U-tube flow path conduit. 

1. A system for operating a well having U-tube flow path conduits therein including: fluid pump means; flow conductors connected to the upper ends of the U-tube flow conduits in the well for conducting fluids from one of the flow conduits in the well to the pump means and from the pump means back into the other conduit of the well for circulating fluids into and out of the U-tube flow path conduits in said well; means for controlling fluid flow through said conductors; fluid pressure operator means connected with the pump means for operating the pump means; means for conducting well fluids from one of the flow conductors connected to the flow conduits in the well to the operator means to drive the operator means to operate the pump means by welL fluid pressure; a supply of fluids for insertion into the well; means connecting the supply of fluid for insertion into the well with the pump means, whereby the fluid from said supply is directed through the pump means into the other flow conductor and into the well flow conduits to fill the U-tube flow path conduits, the flow conductors connected to said conduits, the means for controlling fluid flow through said conductors, and the pump means with fluid from said source of supply of fluid; means for closing off the source of supply of fluid from the U-tube flow path conduits, the flow conductors connected thereto, and said pump means, and for directing well fluids flowing from the well flow conductors to the fluid pressure operator means for actuating the pump means to circulate the fluids therein through the U-tube flow path conduits, the flow conductors connected thereto and the pump means under well fluid pressure.
 2. A system for operating a well having U-tube flow path conduits therein including: fluid pump means; flow conductors connected to the upper ends of the U-tube flow conduits in the well for conducting fluids from one of the flow conduits in the well to the pump means and from the pump means back into the other conduit of the well for circulating fluids into and out of the U-tube flow path conduits in said well; means for controlling fluid flow through said conductors; fluid pressure operator means connected with the pump means for operating the pump means; means for conducting well fluids from one of the flow conductors connected to the flow conduits in the well to the operator means to drive the operator means to operate the pump means by well fluid pressure; a supply of fluid for insertion into the well; means connecting the supply of fluid for insertion into the well with the pump means, whereby the fluid from said supply is directed through the pump means into the other flow conductor and into the well flow conduits; auxiliary pump means having auxiliary drive means operatively connected with said operator means for pumping auxiliary operating fluid to said operator means for actuating the same to operate said pump means when the well fluid pressure is insufficient to actuate said operator means.
 3. A well flow controlling system for use in operating a well having a U-tube flow path conduit therein, said system including: a flow direction controlling manifold at the surface connected to the upper ends of the U-tube flow path conduit for controlling the direction of flow of fluids into and out of said conduit; a source of supply of fluid to be injected into the well U-tube flow path conduit through the manifold; pump means connected to the source of supply of fluid and to the manifold for pumping fluid from the source of supply to the manifold and therethrough into the U-tube flow path conduit in the well; fluid pressure power operator means connected with said pump means for operating the pump means; means for conducting well fluid from the well through the flow directing manifold to the fluid pressure operator means for actuating said operator means by well fluid pressure to drive the pump means to pump fluid from the source of supply into the U-tube flow path conduit by means of said well fluid pressure to fill the U-tube flow path conduit, manifold and pump means with said fluid; means for closing off the source of supply of fluid from the U-tube flow path conduit, manifold and pump means to provide a closed path in the well through the U-tube flow path conduit, manifold and pump means and for continuing to direct fluids flowing from the well to the operator means for operating said pump means by well fluid pressure to circulate the fluids in the closed flow path of the U-tube flow path conduit, manifold and pump means at the pressure of the fluids in the well; and means for conducting the well fluids passing out of said fluid pressure power operator means after operating the same to a place of disposal.
 4. A System of the character set forth in claim 3 wherein: said pump means comprises a cylinder having a piston movable therein; an inlet fluid conduit connected with the source of supply of fluid; an outlet conduit from the cylinder to the flow directing manifold for conducting fluids from the cylinder to the flow directing manifold and to the U-tube flow path conduit in the well; and inlet and outlet conduits each having valve means therein controlling the flow of fluids into and out of the cylinder; and said fluid pressure operator means comprises a cylinder having a larger bore than the bore of the cylinder of the pump means; a piston movable in the cylinder of the operator means having an effective area larger than the effective area of the piston of the pump means; means connecting the power operator means piston with the piston of the pump means for driving the pump piston by means of the power operator means piston; means for conducting well fluids from the flow directing manifold connected with the well U-tube flow path conduit into the power operator cylinder for moving the piston therein to drive the pump means piston; and means connected to the cylinder of the power operator means for conducting the well fluids from said cylinder to said means for conducting said well fluids to a place of disposal after the power operator means piston has been actuated by said well fluids.
 5. A system of the character set forth in claim 4 including: auxiliary pump means having auxiliary drive means operatively connected with said operator means for pumping auxiliary operating fluid to said operator means for actuating the piston of said operator means to operate said pump means when the well fluid pressure is insufficient to actuate said operator means.
 6. A well flow controlling system for use in operating a well having a U-tube flow path conduit therein, said system including: a flow direction controlling manifold at the surface connected to the upper ends of the U-tube flow path conduit for controlling the direction of flow of fluids into and out of said conduit; a source of supply of fluid to be injected into the well U-tube flow path conduit through the manifold; pump means connected to the source of supply of fluid and to the manifold for pumping fluid from the source of supply to the manifold and therethrough into the U-tube flow path conduit in the well; fluid pressure power operator means connected with said pump means for operating the pump means; means for conducting well fluid from the well through the flow directing manifold to the fluid pressure operator means for actuating said operator means by well fluid pressure to drive the pump means to pump fluid from the source of supply into the U-tube flow path conduit by means of said well fluid pressure; means for conducting the well fluids passing out of said fluid pressure power operator means after operating the same to a place of disposal; and auxiliary pump means having auxiliary drive means operatively connected with said operator means for pumping auxiliary operating fluid to said operator means for actuating the same to operate said pump means when the well fluid pressure is insufficient to actuate said operator means.
 7. A well fluid circulating system for use with a well having conduits therein providing two separate longitudinal flow paths therein connected at their lower ends and having flow openings at their upper ends and providing a U-tube flow path conduit in said well communicating with at least one producing formation at the lower end of said well, said system including: a flow direction controlling manifold connected to each of the flow openings of the U-tube flow path conduit of the well and having means for controlling flow direction into and out of said U-tube flow path conduit; a circulating conductor connected to said manifold for receiving fluids from the U-tube flow path conduit in the well; a pump having a cylinder and a piston movable therein for pumping fluids; a supply conDuctor for conducting fluids to be pumped to the pump; a return conductor connected with the pump and with the manifold for conducting fluids to be pumped into the well from the pump to the manifold for direction into the U-tube flow conduit path in the well; a source of supply of fluid to be pumped into the well; means for disposing of fluids from the well; first valve means connected with the circulating conductor, with the supply conductor, with the source of supply of fluid to be pumped into the well and with the means for disposing of fluids from the well; said first valve means being movable to a first position connecting the supply conductor with one of either the source of supply of fluid to be pumped into the well or the circulating conductor connected with the manifold and connecting the means for disposing of fluids with the other of said source of supply of fluid to be pumped or said circulating conductor not connected with the supply conductor; said first valve means being movable to a second position connecting the other of the source of supply of fluid to be pumped or the circulating conductor with the supply conductor, and connecting the means for disposing of fluids with the one of said source of supply of fluid to be pumped and said circulating conductor not connected with the supply conductor; said first valve means when in one of said positions directing fluid from said source of supply of fluid to be pumped to said pump to be pumped into said well U-tube flow path conduit and when in the other of said positions directing fluid from one flow path of the well U-tube flow path conduit to said pump to be pumped into the other flow path of said well U-tube flow path conduit; a fluid pressure power operator device for operating the pump comprising: a cylinder with a power piston movable therein having a cross-sectional area greater than the cross-sectional area of the pump piston; said power piston being operatively connected with the pump piston for actuating the pump piston; second valve means connected with a pair of separate three-way valve means and with a pair of separate inlet conduits into the cylinder of the fluid pressure power operator device on the opposite sides of the power piston therein; one of said three-way valve means being also connected with said circulating conductor and with a supply line from a separate source of hydraulic fluid pressure, whereby when said one three-way valve means is in a first position well fluids from said circulating conductor are directed through said second valve means to said operator device for actuating the piston therein and said supply line from said source of hydraulic fluid pressure is closed, and when said one three-way valve means is in a second position hydraulic fluid pressure from said supply line from said hydraulic fluid pressure source is directed through said second valve means to said operator device for actuating the piston therein and said connection with said circulating conductor is closed; the other three-way valve means being also connected with said means for disposal of fluids and with a return line to said separate source of hydraulic fluid pressure, and movable to a first position to connect said second valve means with said means for disposal of fluids when said one three-way valve means is positioned to connect said second valve means with said circulating conductor whereby well fluids are directed to said operator device to actuate the power piston to operate the pump to pump fluid into the U-tube flow path conduit, and movable to a second position connecting said second valve means with said return line to said hydraulic fluid pressure source and to close the connection with said means for disposal of fluids when said one three-way valve means is positioned to connect said second valve means with said supply line from said source of hydraulic fluid pressure and said circulating conductor is closed, whereby hydraulic fluid pressure is directed through said second valve means to saiD operator device for actuating the power piston therein for pumping fluid into the U-tube flow path conduit in the well, and well fluids from said U-tube flow path conduit are directed to the means for disposal of fluids; and means connected with said power piston of said operator device for actuating said second valve means between positions connecting said one three-way valve means with said cylinder of said operator device alternately on opposite sides of said power piston in said cylinder in response to reciprocating movement of said power piston.
 8. A system for circulating fluids in a well having conduits therein providing two longitudinal flow paths in said well connected near the bottom thereof to form a U-tube flow path for fluids in the well and comprising: pump means for pumping fluids into one of said conduits; operator means for said pump means; conduit means for directing well fluids from the other of said conduits to said operator means, said operator means being responsive to and driven by said well fluids from said other conduit; said pump means having a lesser operating area then the operating area of said pump means, whereby said operator means is operable by said well fluid pressure to operate said pump means to pump fluid into said one conduit; auxiliary pump means having auxiliary drive means operatively connected with said operator means for pumping auxiliary operating fluid to said operator means for actuating said operator means for actuating said operator means to operate said pump means when said well fluid pressure is insufficient to actuate said operator means.
 9. A system of the character set forth in claim 8 including: means for directing fluids pumped into said one of said conduits and into and from the other of said conduits to said pump means and through said pump means back into said one of said conduits in a closed circuit, whereby fluids may be circulated in said closed circuit to carry on pump down tool operations in said U-tube flow path.
 10. A method of operating a well having a U-tube flow path conduit therein including: withdrawing well fluids from the well through one side of the U-tube flow path, utilizing said well fluids to actuate an operator device for operating a fluid pump; and pumping fluids by means of said fluid pump into the other side of the U-tube flow conduit; circulating fluids pumped into the well through said other side of said U-tube flow path into said one side of said U-tube flow path; shutting off flow of well fluids from the well to said operator device; and operating said operator device by a separate source of fluid pressure at the surface of the well to fill the U-tube flow path with liquids pumped thereinto from the surface by said pump.
 11. A method of the character set forth in claim 10 including: the additional step of circulating liquids in the U-tube flow conduit in the well in a closed circuit through the pump.
 12. A method of the character set forth in claim 11 including: the additional step of utilizing the circulating fluids in the closed system to carry out through-the-flow-line pump down tool operations in said U-tube flow path conduit.
 13. A method of the character set forth in claim 10 including: the additional step of pumping another fluid into the U-tube flow path conduit to displace the fluid previously pumped into said U-tube flow path conduit. 